<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style type="text/css">
			.box{
				width: 100px;
				height: 100px;
				transition-property: width;
				transition-duration: 1s;
				transition-delay: 1s;
				transition-timing-function: ease;
				background: red;
			}
			.box:hover{
				width: 200px;
				height: 200px;
			}
		</style>
	</head>
	<body>
		<div class="box"></div>
	</body>
</html>
<script type="text/javascript">
	var last = document.querySelector('li:last-child');
	last.style.background = 'red';
	
</script>